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Problems


IDDescription / TitleSolved By
1
Multiples of 3 and 5
293135
2
Even Fibonacci numbers
241645
3
Largest prime factor
175580
4
Largest palindrome product
160846
5
Smallest multiple
175728
6
Sum square difference
177298
7
10001st prime
150684
8
Largest product in a series
133139
9
Special Pythagorean triplet
132727
10
Summation of primes
121009
11
Largest product in a grid
90977
12
Highly divisible triangular number
81296
13
Large sum
88195
14
Longest Collatz sequence
86000
15
Lattice paths
71183
16
Power digit sum
92083
17
Number letter counts
59223
18
Maximum path sum I
58865
19
Counting Sundays
53888
20
Factorial digit sum
86331
21
Amicable numbers
58249
22
Names scores
54364
23
Non-abundant sums
40446
24
Lexicographic permutations
47434
25
1000-digit Fibonacci number
64471
26
Reciprocal cycles
33367
27
Quadratic primes
35268
28
Number spiral diagonals
48608
29
Distinct powers
42696
30
Digit fifth powers
45606
31
Coin sums
32831
32
Pandigital products
28531
33
Digit canceling fractions
29966
34
Digit factorials
40054
35
Circular primes
36654
36
Double-base palindromes
39385
37
Truncatable primes
30666
38
Pandigital multiples
25952
39
Integer right triangles
30176
40
Champernowne's constant
34010
41
Pandigital prime
28307
42
Coded triangle numbers
33131
43
Sub-string divisibility
23600
44
Pentagon numbers
22863
45
Triangular, pentagonal, and hexagonal
31514
46
Goldbach's other conjecture
24157
47
Distinct primes factors
23672
48
Self powers
54142
49
Prime permutations
23154
50
Consecutive prime sum
25009